Preparation of silicon halides



Patented 1m 21, 1949 PATENT 7 OFFICE rnarsnarron or slmcos muons Arthur J.

and Lee Barry. (1 '1 In! D. EST-mime,

The Dow Chemical Company, Midland, Mich, a corporation of, Delaware No Drawing. Application May Serial No. 748,846

Claims. '(01. zen-ma) This invention relates to a new process for the preparation of halogen-substituted monosilanes. It is particularly concerned with the preparation of monosilanes having a plurality of halogen atoms attached to the single silicon atom in the molecule, such as silicon tetrahalides, trihalosilanes of the type HSiXa, monoalkyltrihalosilanes, haloalkyltrihalosilanes, aryltrihalosilanes, and haloaryltrihalosilanes.

. It has been found that a polyhalopolysilane may be reacted with a halohydrocarbon to produce halogen-substituted monosilanes.

Polyhalopolysilanes which may be employed for purposes of this invention are inorganic silicon halides containing at least one silicon-silicon bond, all 'valences of silicon which are not satisfled by such linkage to other silicon atoms being taken up by halogen atoms. Examples of suitable polyhalopolysilanes include hexachlorodisilane, S12Cla, hexabromodisilane, SizBra, octachlorotrisilane, SisCls, decachlorotetrasilane, Si4Cl1o, or mixtures of such inorganic silicon halides.

Examples of suitable halohydrocarbons include alkyl halides such as methyl chloride, methyl bromide, ethyl chloride, ethyl bromide, dichloroethane, prcpyl chloride, propyl bromide, butyl chloride, lauryl chloride, and polychloroalkanes,

and aromatic halohydrocarbons such as chlorobenzene and dichlorobenzene. f

Catalysts for the formation of carbon-silicon bonds, such as cuprous chloride, antimony'tri-- chloride, or mercuric chloride, may be added'to the starting materials if desired. When employed, such catalyst is usually present in minor amount, e. g. from 1 to 2 parts by weight thereof per 100 parts of halohydrocarbon and polyhalopolysilane.

In general, the reaction between a halohydrocarbon and a polyhalopolysilane is advantageously carried out at a temperature between 100 and 450 C. When an alkyl halide is employed as the halohydrocarbon, it is preferred to conduct the reaction at a temperature below about 350 C. When the halohydrocarbon starting material is an aryl halide, it is usually advantageous to carry out the reaction at a temperature above about 300 0., to ensure an adequate rate of reaction. Operating under the conditions stated above, 'interaction between the indicated reactants is ob- 5 tained.

The-reaction is conducted at a gauge pressure of at least 5 atmospheres. This may be obtained either by introducing the reactants into the reaction zone under reaction conditions under pressure, or by operating under autogenous pressure in a closed system. The reaction is preferably conducted under conditions such that at least a portion of the re- 6 actants is in liquid phase. Thus, for example, the reaction may be eilected in the presence of a mutual solvent, e. g. a paramn oil. Frequently, one or more of the reactants is liquid under the reaction conditions, and may serve as a solvent 10 for other starting materials. With some particular reactants, at temperatures within the range indicated, pressures below 5 atmospheres may be employed when some liquid phase is obtained therewith.

The overall reaction between a polyhalopolysilane and a halohydrocarbon may be illustrated by the following equation:

where R is a monovalent organic radical connected to the silicon through a carbon-silicon bond. In some instances, other products, such as elemental silicon, or a hydrocarbon may also be produced.

As illustrated in the molecular equivalent equation above, for each weight of polyhalopolysilane entering into reaction, one molecular equivalent weight of halohydrocarbon is required. Although it is generally preferred to employ approximately equimolecular equivalent ratios of the reactants, much greater or less proportions may also be employed, e. g. from 0.5 to 3.0 mols .of halohydrocarbon per mol of polyhalopolysilane.

The following examples serve to illustrate the process of this invention, but are not to be construed as limiting its scope:

EXAMPLE 1 A mixture comprising 0.56 gram molecular equivalent weight of hexachlorodisilane and 0.50 gram mol of ethyl chloride was placed in a bomb of 500 milliliter capacity. The bomb and contents was heated at from 263 to 277 C. for about 16 hours. Thereafter, the bomb was cooled .45 to approximately room temperature and the contents collected and condensed. Subsequently, the product was fractionally distilled. There was obtained approximately 0.12 gram mol of ethyltrichlorosilane, and 0.24 gram mol of silicon tetrachloride. Unreacted hexachlorodisilane was recovered.v

Exams: 2 A 500 milliliter bomb was loaded with epproximately 0.50 gram mol of hexachlorodisilane, 1

0.75 gram mol of ethyl gram mol of cuprous chloride. The bomb was then heated for 16 hours at 318-B37. C., during which time the maximum pressure developed chloride, and about 0.03

The experiment described in Example 2 was repeated, except that mercuric chloride (3 grams) was employed instead of cuprous chloride. There within the bomb was 1110 pounds per square 5 btained approximately 0.64 gram mols of inch. The products were recovered as in Exwas ample 1. There was obtained approximately 0.30 i g tetaachmnde and gram mols of ethyl gram mol of ethyltrichlorosilane, and 0.56 gram r 6 mol of silicon tetrachloride. EXAMPLE 8 Exli a 10 A mixture comprising about 99 percent by 1 weight of 1,4-dichlorobutane and hexachlorodi- 5; g :32 :55?lgg g gg ffi' ggg g E's silane' in equimolecular proportions, and about 0.50 gram mol of hexachlorodisilane were re- 3 n?i g jf gfg f fi gfif g fi sg m z acted in the presence of cuprous chloride, and e p the products were collected and purified by trac of reactlon were collected and fractionally distionai distillation. There was obtained 0.48 gram f f' i z tetrachloride and tmcmomsnane mol of silicon tetrachloride and 0.36 gram mol of gf g this invention may be monobromotncmomsnane' ployed other than those specifically disclosed in EXAMPLE 4 the examples without departing from the spirit 11.4 parts by weight of a mixture of higher afia g s following alkyl chlorides, consisting for the most part of 1 ig c fig f i dodecyl chloride and tetradecyl chloride, was rei g ggs; s f zggg acted with 10 parts of hexachlorodisllane in av alk lhande and aromati hal h r M n n bomb. The products were collected and frach 1 yd 9; b0 d tionally distilled. Silicon tetrachloride was obg g g g 35 tained as well as a material distilling wi t iin the are i satisfied 3 3 zfi g 2 ig in a d cim in itlg zfi 21 2 3321 being taken up by en atoms, in liquid of hydrolyzable chlorine. This material contains g g'gf ggg gz figsfigg g zggi igg 5 22 2332 si zz gg g g g 32 323 together with organic radical attached to the single silicon atom in the molecule through a carbon-silicon bond. EXAMPLE 5 2. The method of making a polyhalomonosilane, By procedure similar to that described in the containing a monovalent organic radical attached preceding examples, various halohydrocarbons to fi g fi g L molefule gs and polychloropolysilaries were rteacted. In eacl; ig igg ggi g g isgi gg i f instance, approximate y par by weight 0 alk l halides and aromatic haloh drocarbons g g g g gg gg i xii gii ia 333 522 33: and? an inorganic silicon halide c ntaining a sflane emp1oyed silicon-silicon linkage, all valences of the silicon The following table names the reactants emgg g' m i z f to ployed in each experiment, states the molecular 0 er 5 won a i eng 1 5: 2 ogen proportions in which they were used, gives the atoms at t empera we of from temperature at which the bomb was heated. least a portion of the reactants being 1n the liquid states the maximum pressure, expressed as pounds P per square inch, developed within the bomb, and The method of making a p y alomofl names the compounds constituting the major silane, containing a monovalent organic radical portion of the product obtained'by each reaction. attached to the single silicon atom in the mole- Table Halohydrocarbon Polyhalopolysilane Run No. T9116?" PE??? Major Products Kind Niols Kind Mola- 1 v n-propyltricbiorolsilane n-propylchloride 0.75 hexachlorodlsilane... 0.50 311-333 930 silicon tetrachloride 2 iso-propyl chloride 0.75 do .0-50 3- 0 afigggkggfiggggag ll' 0 fl 0 0518116 3 n-propyl bromide 0.75 do 0- 2 1.080 {g fi gg f gfigggg 4 chlorobenzene 0.56 do 0. 8 -37 0 {g gg g gglgfif gg 5 orthodich1orobonzene 0.75 do 0- 50 3 400 gfiigg l g gg fi ggg 0 ethyl chloride 0.83 octacblorotrisilane..-" 0- 311-339 8 [3 3:3 ,gglggfiflggg EXAMPLE 6 cule through a carbon-silicon bond, which comprises reacting an alkyl halide and an inorganic The Procedure of Example 2 was repeated with silicon halide containing a silicon-silicon bond,

the exception that antimony trichloride (3 grams) was employed instead of cuprous chloride. There was obtained approximately 0.62 gram mols of silicon tetrachloride and 0.16 gram mols of ethyltrichlorosilane.

all valences of the silicon atoms which are not satisfied by such linkage to other silicon atoms being taken up'by halogen atoms, at a temperature of from 100 to 350 C., at least a portion of the reactants being in'the liquid phase.

4. The method of making a polyhalomonosilane, containing a. monovalent organic radical attached to the single silicon atom in the molecule through a carbon-silicon bond, which comprises reacting an alkyl h'alide and an inorganic silicon halide containing a silicon-silicon bond, all valences of the silicon atoms which are not satisfied by such linkage to other silicon atoms being taken up by halogen atoms, at a temperature of from 100 to 350 C., under pressure of at least 5 atmospheres.

5. The method of making a polyhalomonosilane, containing a monovalent organic radical attached to the single silicon atom in the molecule through a carbon-silicon bond, which comprises reacting an aromatic halohydrocarbon and an inorganic silicon halide containing a siliconsilicon bond, all valences of the silicon atoms which are not satisfied by such linkage to other REFERENCES CITED v The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date OTHER REFERENCES Volnov: Journal Gen. Chem., U. S. S. R. (1940), vol. 10, pages 1600-1604.

Miller July 3, 1945 

